ktest: introduce grub2bls REBOOT_TYPE option

Fedora 30 introduces Boot Loader Specification (BLS),
it changes around grub entry configuration.

kernel entries aren't in grub.cfg. We can get the entries
by "grubby --info=ALL" command.

Introduce grub2bls as REBOOT_TYPE option for BLS.

Link: http://lkml.kernel.org/r/20190509213647.6276-4-msys.mizuma@gmail.com



Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>